"Criticism of Israel indicates engagement with Israel. American Jews should be worried when their children stop criticizing Israel," says Professor Steven Cohen, a sociologist of American Jewry on the faculty at Hebrew Union College-Jewish Institute of Religion in New York.

Tenafly, New Jersey, is a suburb of 16,000 people, nearly half of them Jewish, just across the Hudson River from New York City. However, when a group of Orthodox Jewish newcomers put up a symbolic boundary called an eruv, Tenafly became one of the latest battlegrounds in an ongoing civil war in the American Jewish community.